High-intensity interval training combining rowing and cycling improves but does not restore beta-cell function in type 2 diabetes

Houborg Petersen M, Stidsen JV, Eisemann de Almeida M, Kleis Wentorf E, Jensen K, Ørtenblad N, Højlund K

Question

Can 8 weeks of supervised HIIT combining upper- and lower-body exercise restore beta-cell function in men with type 2 diabetes compared with obese and lean glucose-tolerant controls?

Summary

In sedentary middle-aged men with type 2 diabetes and glucose-tolerant obese or lean controls, 8 weeks of supervised HIIT combining rowing and cycling improved insulin sensitivity in all groups. Beta-cell function adjusted for insulin sensitivity improved substantially but variably in type 2 diabetes, yet remained markedly impaired compared with controls.

Methodology

Sedentary middle-aged men with type 2 diabetes, obese glucose-tolerant controls, and lean glucose-tolerant controls
48 participants.
Alternating rowing and cycling ergometer intervals.
Work intervals: 1 min high-intensity interval.
Recovery: 1 min active or passive recovery between intervals; 4 min break between blocks.
Intensity: >=85% HRmax during intervals.
10 min warm-up plus 2-5 training blocks and 4 min breaks.
3 sessions/week.
8 weeks.
Prespecified secondary analysis of a controlled training study with pre-post within-group comparisons
Disposition index, Insulin sensitivity, Insulin secretion, and Free fatty acids were tracked.

Outcomes

Insulin sensitivity

HIIT increased insulin sensitivity in all groups.

All groups p < 0.01

Improved

Disposition index

Disposition index improved substantially but variably in type 2 diabetes and modestly in controls.

Type 2 diabetes >200% improvement, p < 0.05; controls about 20-30%, p < 0.05

Improved

Beta-cell restoration

Despite improvement, disposition index remained markedly lower in type 2 diabetes than controls.

Post-HIIT type 2 diabetes DI remained lower than controls, all p < 0.001

No clear change

Second-phase insulin

Second-phase insulin responses were reduced after HIIT in all groups.

All groups p < 0.05; authors interpret in context of improved insulin sensitivity

Safety concern

Adherence

Attendance and achieved interval intensity were high, with no injuries reported.

Attendance >95% in all groups; average HRmax above 85% during intervals; no participants sustained injuries

Improved

Insights

Combining rowing and cycling can recruit upper and lower body muscle groups in HIIT.
HIIT can improve insulin sensitivity, but beta-cell dysfunction in established type 2 diabetes may not normalize.
Clinical metabolic testing occurred about 60 h after the last HIIT session to reduce acute exercise confounding.

Limitations

Men only
No non-exercise randomized control arm in this analysis
Clinical laboratory protocol with rowing/cycling ergometers
Secondary analysis
Beta-cell outcomes require specialized clamp/IVGTT methods

Safety

No participants sustained injuries; four participants dropped out during the project, including one lean man before training due to a new knee injury and three for lack of time.